5 research outputs found
Site Diversity in Downlink Optical Satellite Networks Through Ground Station Selection
Recent advances have shown that satellite communication (SatCom) will be an
important enabler for next generation terrestrial networks as it can provide
numerous advantages, including global coverage, high speed connectivity,
reliability, and instant deployment. An ideal alternative for radio frequency
(RF) satellites is its free-space optical (FSO) counterpart. FSO or laser
SatCom can mitigate the problems occurring in RF SatCom, while providing
important advantages, including reduced mass, lower consumption, better
throughput, and lower costs. Furthermore, laser SatCom is inherently resistant
to jamming, interception, and interference. Owing to these benefits, this paper
focuses on downlink laser SatCom, where the best ground station (GS) is
selected among numerous candidates to provide reliable connectivity and maximum
site diversity. To quantify the performance of the proposed scheme, we derive
closed-form outage probability and ergodic capacity expressions for two
different practical GS deployment scenarios. Furthermore, asymptotic analysis
is conducted to obtain the overall site diversity gain, and aperture averaging
is studied to illustrate the impact of aperture diameter on the overall
performance. Finally, important design guidelines that can be useful in the
design of practical laser SatComs are outlined
Evolution of High Throughput Satellite Systems: Vision, Requirements, and Key Technologies
High throughput satellites (HTS), with their digital payload technology, are
expected to play a key role as enablers of the upcoming 6G networks. HTS are
mainly designed to provide higher data rates and capacities. Fueled by
technological advancements including beamforming, advanced modulation
techniques, reconfigurable phased array technologies, and electronically
steerable antennas, HTS have emerged as a fundamental component for future
network generation. This paper offers a comprehensive state-of-the-art of HTS
systems, with a focus on standardization, patents, channel multiple access
techniques, routing, load balancing, and the role of software-defined
networking (SDN). In addition, we provide a vision for next-satellite systems
that we named as extremely-HTS (EHTS) toward autonomous satellites supported by
the main requirements and key technologies expected for these systems. The EHTS
system will be designed such that it maximizes spectrum reuse and data rates,
and flexibly steers the capacity to satisfy user demand. We introduce a novel
architecture for future regenerative payloads while summarizing the challenges
imposed by this architecture
1-D broadside-radiating leaky-wave antenna based on a numerically synthesized impedance surface
A newly-developed deterministic numerical technique for the automated design of metasurface antennas is applied here for the first time to the design of a 1-D printed Leaky-Wave Antenna (LWA) for broadside radiation. The surface impedance synthesis process does not require any a priori knowledge on the impedance pattern, and starts from a mask constraint on the desired far-field and practical bounds on the unit cell impedance values. The designed reactance surface for broadside radiation exhibits a non conventional patterning; this highlights the merit of using an automated design process for a design well known to be challenging for analytical methods. The antenna is physically implemented with an array of metal strips with varying gap widths and simulation results show very good agreement with the predicted performance
Beam scanning by liquid-crystal biasing in a modified SIW structure
A fixed-frequency beam-scanning 1D antenna based on Liquid Crystals (LCs) is designed for application in 2D scanning with lateral alignment. The 2D array environment imposes full decoupling of adjacent 1D antennas, which often conflicts with the LC requirement of DC biasing: the proposed design accommodates both. The LC medium is placed inside a Substrate Integrated Waveguide (SIW) modified to work as a Groove Gap Waveguide, with radiating slots etched on the upper broad wall, that radiates as a Leaky-Wave Antenna (LWA). This allows effective application of the DC bias voltage needed for tuning the LCs. At the same time, the RF field remains laterally confined, enabling the possibility to lay several antennas in parallel and achieve 2D beam scanning. The design is validated by simulation employing the actual properties of a commercial LC medium